centerline butterfly valve Archives

Stem structure of centerline wafer butterfly valve

July 11, 2022

The centerline wafer butterfly valve can be divided into two types: pinless butterfly valve and pinned butterfly valve. The main difference between them is whether the valve plate and the valve stem are fixed with a pin. The pinned butterfly valve and the pinless butterfly valve

JIS 10K-wafer butterfly valve-backup seat (3)

correspond to the needs of different working conditions, and more depends on the needs of users. Because the process of the pinless butterfly valve is more effective and more complicated, and there is no pin hole on the surface of the butterfly plate, its price is also a little more expensive than that of the butterfly valve with a pin. And relatively speaking, it does not appear pitting corrosion and point leakage. Now let’s take a look at the pinless structure of the centerline wafer butterfly valve:

Centerline Wafer Type Butterfly Valve Double Half Shaft Structure
The double half shaft is a kind of structural performance of the midline wafer butterfly valve, also called the square shaft. Corresponding to it is the through shaft. Double semi-shaft means that there is a shaft on the upper and lower sides of the valve plate of the butterfly valve. The upper shaft and the valve stem are integrally formed to act as a transmission, and the lower shaft is a circular shaft, which plays the role of positioning the valve plate. Since the connection between the upper shaft, the valve stem and the valve plate is usually through a square shaft – a square hole, there are also hexagonal connections. Therefore, the processing of the valve plate is usually processed by punching, slotting or EDM, and the processing efficiency is low. In addition, the lower shaft also needs to pass through the through hole at the bottom of the valve body to be installed. After that, it is necessary to add a gasket and a retaining ring to the bottom to fix the lower shaft. The processing and assembly of the valve body also increases the difficulty. Therefore, this structure is only used in large sizes now.

Large and small head shaft structure of centerline wafer butterfly valve
The stem of this midline wafer butterfly valve is a flat shaft that passes through the valve plate. The diameter at the lower end is reduced to a size smaller than the flat hole of the valve plate to pass through the valve plate, and the bottom of the valve body is used for positioning to ensure the valve Concentricity and symmetry of the plate. The processing of the through hole of the valve plate only requires a high degree of coaxiality of the single-side feed. In addition, there is no through hole at the bottom of the valve body, which also avoids external pollution caused by the leakage of the valve body. However, due to the variable diameter of the valve stem and the valve body, the processing cost is appropriately increased, and the upper and lower holes of the valve seat are not of equal diameter, which is also prone to errors in the assembly process.

Equal Diameter Flat Shaft for Centerline Wafer Type Butterfly Valve
The structure of this midline wafer butterfly valve is evolved from the structure of the large and small head shafts. The valve stem is an equal-diameter shaft. The bottom is processed into double D type and the valve plate forms a close fit to ensure the transmission of the valve plate. It is also a flat hole, but the direction of the flat hole is rotated by a 90°, so as to ensure that when the valve is at the closing point or close to the closing point, the valve stem is in contact with the valve body bushing with a circular surface to ensure the symmetry of the valve plate and the same The axial degree can not only avoid the bending deformation of the valve stem but also make the valve close tightly. Since the valve body and seat are the same size in both directions, the efficiency can be greatly improved during processing and assembly. This kind of structure is simple and practical, and has the characteristics of high processing efficiency, quick assembly, tight coordination, economical saving and so on.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Characteristics of the centerline wafer butterfly valve

October 14, 2021

The centerline wafer butterfly valve is one of the commonly used butterfly valves. It is named because of the structure of the stem axis, the center of the butterfly plate and the center of the body at the same position. The structure of the centerline butterfly valve is very simple, and the installation and maintenance are also very

Wafer type butterfly valve with worm gear

convenient. As a component that controls the on-off and flow rate of the pipeline system, the centerline clamp valve is widely used in pipeline systems in the fields of petroleum, chemical industry, hydropower station, municipal construction, water supply and drainage.
The sealing form of the centerline wafer butterfly valve is generally a soft seal, and the sealing material is rubber or polytetrafluoroethylene, so the centerline wafer butterfly valve is usually a soft sealing butterfly valve. Therefore, the advantages of this type of valve are that the seal can be replaced, the sealing performance is excellent and reliable, zero leakage can be achieved, and two-way sealing can be achieved. . However, due to the limitation of its own structural characteristics, the centerline wafer butterfly valve also has some shortcomings. Because the butterfly plate and valve seat of the valve are always in a state of squeezing and scratching, the resistance distance is large, and the wear on the butterfly plate and valve seat is very large, so In order to overcome the phenomenon of squeezing and scratching and ensure the sealing performance of the valve, the valve seat of the centerline butterfly valve adopts elastic materials such as rubber or polytetrafluoroethylene to ensure the sealing performance of the valve. However, materials such as banana and polytetrafluoroethylene are subject to temperature restrictions in use. Therefore, the disadvantage of the centerline butterfly valve is that it is not resistant to high temperatures.
The centerline wafer butterfly valve is not suitable for high temperature and high pressure working environment, has poor wear resistance and short service life. These shortcomings make the scope of application of the valve have certain limitations. In order to overcome this problem, there is now a triple eccentric metal hard seal butterfly valve, which is different from the centerline wafer butterfly valve. The stem axis of the triple eccentric butterfly valve deviates from the center of the butterfly plate and the center of the body at the same time, and the rotation axis of the valve seat and the axis of the valve body channel There is a certain angle. Compared with the centerline butterfly valve, the triple eccentric butterfly valve is more resistant to high temperature, and also has good sealing performance and longer service life.
The valve body and the valve seat are connected components, and the sealing surface layer of the valve seat is welded with temperature-resistant and corrosion-resistant alloy materials. The multi-layer soft laminated sealing ring is fixed on the valve plate. Compared with the traditional butterfly valve, this butterfly valve has high temperature resistance, light operation, no friction when opening and closing, and when closing, the torque of the transmission mechanism increases to compensate for the sealing, which improves the butterfly valve. The advantages of sealing performance and extended service life.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Detailed introduction of soft sealing butterfly valve-(3)

July 28, 2020

Features of soft sealing butterfly valve:

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

1. Small and light, easy to disassemble and repair, and can be installed in any position.

2. The structure is simple and compact, the operating torque is small, and the 90-degree rotation opens quickly.

3. The flow characteristics tend to be straight, and the regulation performance is good.

4. The connection between the butterfly plate and the valve stem adopts a pinless structure, which overcomes possible internal leakage points.

5. The seal can be replaced, and the seal is reliable to achieve two-way sealing.

6. The butterfly plate can be sprayed with a coating layer, such as nylon or PTFE, according to user requirements.

7. The valve can be designed as flange connection and wafer connection.

8. The driving mode can be manual, electric or pneumatic.

Problems in the use of soft sealing butterfly valves:

1. Due to the principle of the triple eccentric structure, the sealing between the sealing surface of the valve plate and the valve seat is to press the valve plate against the valve seat by the torque of the transmission device. In the state of positive flow, the higher the medium pressure, the tighter the sealing extrusion. When the flow channel medium flows back, as the medium pressure increases, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal begins to leak.

2. Due to structural conditions, this structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate is too thick and the flow resistance is large.

3. Since the multilayer soft and hard stacked sealing ring is fixed on the valve plate, when the valve plate is normally open, the medium will wash its sealing surface positively, and the soft sealing tape in the metal sheet sandwich will directly affect the sealing performance after being washed.

high-performance soft sealing butterfly valve, characterized in that: the valve seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of the soft T-shaped sealing ring.

The sealing surface of the valve plate and the valve seat is of an oblique cone structure, and the oblique cone surface of the valve plate is welded with temperature-resistant and corrosion-resistant alloy materials; the spring fixed between the adjusting ring pressure plate and the adjusting bolt of the pressure plate are assembled together. This structure effectively compensates for the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure, and solves the sealing problem of the valve in the two-way interchangeable medium conveying process.

The sealing ring is composed of a soft T-shaped multi-layer stainless steel sheet on both sides, which has the dual advantages of metal hard and soft sealing. It has zero leakage sealing performance regardless of low temperature and high temperature. The test proves that in the positive flow state of the pool (the flow direction of the medium is the same as the rotation direction of the butterfly plate), the pressure of the sealing surface is produced by the torque of the transmission device and the action of the medium pressure on the valve plate. When the positive medium pressure increases, the tighter the oblique cone surface of the valve plate and the sealing surface of the valve seat are pressed, the better the sealing effect.

Therefore, unlike the prior art, the utility model does not install a soft and hard multilayer sealing ring on the valve plate, but directly installs it on the valve body. Adding an adjustment ring between the pressure plate and the valve seat is a very ideal two-way hard sealing method. . It can replace gate valves and ball valves.

In the reverse flow state, the seal between the valve plate and the valve seat is pressed against the valve seat by the torque of the driving device. With the increase of the reverse medium pressure, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the adjusting ring after being loaded compensates for the tight pressure of the sealing surface of the valve plate and the valve seat Play the role of automatic compensation.

Detailed introduction of soft sealing butterfly valve-(2)

July 28, 2020

There are many types of soft-sealed butterfly valves, which can be divided into the following categories according to different forms:
Classified by structure
Classified by structure

(1) Center sealing butterfly valve

(2) Single eccentric sealed coal valve

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

(3) Double eccentric sealing butterfly valve

(4) Triple eccentric seal valve

Classified according to the sealing surface material:

(1) Soft sealing butterfly valve.

1) The sealing pair is composed of non-metallic soft material to non-metallic soft material.

2) The sealing pair is composed of a metal hard material and a non-metal soft material.

(2) Metal hard seal butterfly valve. The sealing pair is composed of a metal hard material to a metal hard material.

Classified according to the sealing form:

(1) Forced sealing butterfly valve

1) Elastic sealing butterfly valve. The specific pressure of the seal is generated by the valve plate squeezing the valve seat when the valve is closed, and the elasticity of the valve seat or valve plate

2) External torque sealing butterfly valve. The seal specific pressure is generated by the torque applied to the valve shaft

(2) Pressurized sealing butterfly valve. The specific sealing pressure is generated by the pressure of the elastic sealing element on the valve seat or valve plate

(3) Automatic sealing butterfly valve. The sealing specific pressure is automatically generated by the medium pressure.

Classified by work pressure:

(1) Vacuum butterfly valve. Butterfly valves whose working pressure is lower than the atmospheric pressure of the standard reactor.

(2) Low pressure butterfly valve. Butterfly valve with nominal pressure PN<1.6MPa.

(3) Medium pressure butterfly valve. Butterfly valve with nominal pressure PN of 2.5-6. 4MPa.

(4) High pressure butterfly valve. A butterfly valve with a nominal pressure PN of 10.0-80.0MPa.

(5) Ultra-high pressure butterfly valve. Butterfly valve with nominal pressure PN>100MPa.

Classified by working temperature:

(1) High temperature butterfly valve. t>450 C butterfly valve

(2) Medium temperature butterfly valve. 120 C＜t＜450 C butterfly valve

(3) Normal temperature butterfly valve. One 40C<t<; 120 C butterfly valve

(4) Cryogenic butterfly valve. One 100＜t＜一40 C butterfly valve

(E) Ultra-low temperature butterfly valve. t＜一100 C butterfly valve

Classified according to the connection method:

(1) Wafer butterfly valve

(2) flange butterfly valve

(3) lug butterfly valve

(4) Welded butterfly valve

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